That said, this definitely sounds like "We'll give you $50 bucks so that we can start reselling it since the rights are ours anyways. Thanks Chumps!"
[0] - http://www.monkeyinthecage.com/wp-content/uploads/2012/07/Ta...
I dunno, how much do you think they'll make off of a random adventure from 30 years ago? More than $50, sure—but it's not like this is highway robbery.
1.) Make a derivative work for the new D&D version (everyone loves retro)
2.) Make a new video game off of the old content.
3.) Rerelease books are part of an XXst aniversary edition.
The key here being that "they" (since it wasn't really WotC, but TSR) lost a lot of physical assets (both written and visual IP), and are basically paying pocket change for people to give that back to them. Indeed, they are even having the end user do the hardest part of the work, which is the scanning. Rather than just buying the books at market prices, and then doing the work themselves.
The real question is, "Why would they ask for scans of old books and pay $50 for them", with the only commercially reasonable answer being, "Because they think that they will obtain much more that $50 woth of value, or the work required to obtain and scan it themselves is worth way more than $50".
If you think this is a ripoff ("Thanks, chumps!"), the only possible conclusion is that any time anyone gives you money for anything, you're getting ripped off.
The alternative, sane model is known as the gains from trade. https://en.wikipedia.org/wiki/Gains_from_trade
It's a normative argument about the appropriate distribution of the gains from trade.